Essen, Univ., Diss., 2001. / Computerdatei im Fernzugriff.

Essen, Univ., Diss., 2001. / Computerdatei im Fernzugriff.

Essen, University, Diss., 2001.

Zugl.: Darmstadt, Techn. Univ., Diss., 2008

University, Diss., 2002--Dortmund.

According to numerous sources, computer security can be explained as; how to address the three major aspects, namely Confidentiality, Integrity and Availability. Public-key infrastructure is a certificate based technology used to accomplish these aspects over a network. One major concern involving PKIs is the way they handle revocation of invalid certificates. The proposed solution will make revocation more secure; validation will be handled completely by the certificate authority, and revokes will be instant, without use of certificate revocation lists. / I enlighet med flertalet källor, kan datorsäkerhet beskrivas som; hur man adresserar de tre mest betydelsefulla aspekterna, nämligen Confidentiality (Tillit), Integrity (Integritet) och Availability (tillgänglighet). PKI är en certifikat baserad teknologi som används för att uppfylla dessa aspekter över ett nätverk. Ett huvudsakligt orosmoment rörande PKI är hur man skall hantera annullering av ogiltiga certifikat. Den föreslagna lösningen kommer att hantera annullering på ett mer säkert sätt; validering av certifikat hanteras uteslutandes av ”certifikat instansen” (the certificate authority), och annulleringar sker omedelbart, utan användning av ”annullerings listor” (certificate revocation lists).

Many network operators need to be able to ensure that customers get the level of service they pay for. To avoid bandwidth and server performance bottlenecks, and easily troubleshoot network problems, the network providers need to be able to see what payload data is sent. Modern networks encrypt data when sending it between nodes that makes passive monitoring more complex. A prevalent encryption mechanism on an IP-based network is TLS that needs to be decrypted.                This article’s purpose is to check if it is possible to decrypt TLS traffic in a passive monitoring system with the server’s private key. This is done by implementing a decryptor in a passive monitoring system in the programming language Java. The implemented solution intercepts the traffic, takes out relevant data from the traffic, and derives the session key from that data. How this is done is dependent on what cipher suite is used for the session. Because of delimitations and lack of time the solution is only able to decrypt the cipher suite TLS_RSA_WITH_AES_128_CBC_SHA256. The result showed that it is possible to decrypt TLS traffic and should be possible for more than the specified cipher suite. But there exists a major problem that's called forward secrecy. This is used in the key exchange algorithm called Diffie–Hellman and makes it impossible to decrypt with only server private key. The conclusion is that it is possible but because of forward secrecy, it is not recommended. TLS 1.3 only uses cipher suites with the key exchange algorithm Diffie–Hellman and the forward secrecy functionality is important for security.

The emerging Blockchain technology has the potential to shift the traditional centralized systems to become more flexible, efficient and decentralized. An important area to apply this capability is supply chain. Supply chain visibility and transparency has become an important aspect of a successful supply chain platform as it becomes more complex than ever before. The complexity comes from the number of participants involved and the intricate roles and relations among them. This puts more pressure on the system and the customers in terms of system availability and tamper-resistant data. This thesis presents a private and permisioned application that uses Blockchain and aims to automate the shipping processes among different participants in the supply chain ecosystem. Data in this private ledger is governed with the participants’ invocation of their smart contracts. These smart contracts are designed to satisfy the participants’ different roles in the supply chain. Moreover, this thesis discusses the performance measurements of this application results in terms of the transaction throughput, transaction average latency and resource utilization. / Graduate

This thesis describes principles of specific HTTPS attacks and provides realization of attacks using lab environment based on VMware. Elaboration is divided to specific dedicated attacks, each part evaluates risk of vulnerability and describes the way of realization in guides for students and lector´s manuals.

The Rijndael cipher was chosen as the Advanced Encryption Standard (AES) in August 1999. Its internal structure exhibits unusual properties such as a clean and simple algebraic description for the S-box. In this research, we construct a scalable family of ciphers which behave very much like the original Rijndael. This approach gives us the opportunity to use computational complexity theory. In the main result, we generate a candidate one-way function family from the scalable Rijndael family. We note that, although reduction to one-way functions is a common theme in the theory of public-key cryptography, it is rare to have such a defense of security in the private-key theatre. In this thesis a plan of attack is introduced at the circuit level whose aim is not break the cryptosystem in any practical way, but simply to break the very bold Rijndael security claim. To achieve this goal, we are led to a formal understanding of the Rijndael security claim, juxtaposing it with rigorous security treatments. Several of the questions that arise in this regard are as follows: ``Do invertible functions represented by circuits with very small numbers of gates have better than worst case implementations for their inverses?' ``How many plaintext/ciphertext pairs are needed to uniquely determine the Rijndael key?'